/Engine/Plugins/Experimental/MeshModelingToolsetExp/Source/ModelingEditorUI/Public/ModelingWidgets/SToolInputAssetPicker.h
Unless you are really certain you need to use this class directly, it's likely that you are looking forSToolInputAssetComboPanel, which provides a combobox/flyout-style widget suitable for user interface panels.
class SToolInputAssetPicker : public [SCompoundWidget](API\Runtime\SlateCore\Widgets\SCompoundWidget)